Yes It works. Once you deposit the needed fee in the account you have signed up, ViaBTC will deduct it and make your transaction a priority in the next block they(ViaBTC) will mine.
But I got to be honest, 0.0029925 BTC is one hell of a high fee even at the moment only that you probably have no choice and you want the transaction to be confirmed as soon as possible. If you had paid the optimal fee earlier on or enabled RBF, you would pay far less than what ViaBTC accelerator is suggesting you to pay them to accelerate your transaction.